12/2/2012 12:30 PM PST

There can only be one "PERSIAN BARBIE" ... so says a smokin' hot model who claims Bravo's show "Shahs of Sunset" is illegally using HER moniker for one of their cast members.

Niki Ghazian (left) -- FHM model and self-proclaimed "Persian Barbie" -- fired off a cease and desist letter last week to Bravo honchos ... claiming the network has no right to use the term for its newest star Lilly Ghalichi (right).

FYI -- Lilly's co-stars refer to her as the "Persian Barbie" on the show ... which Bravo has utilized in promos and on Lilly's official bio.

Niki says that's not okay -- and while she never applied for a trademark, she says she's the "common law owner" ... claiming ever since 2005, publications like FHM, Kandy Mag, NYLA Mag and more have used it to describe her.

Niki is demanding Bravo stop using the term ASAP -- and remove it from their ads, website and any other press releases ... or else.